Ignition composition



Patente cl July 9, 1935 UNITED STATES PATENT OFFICE IGNITION COMPOSITION Charles P. Spaetli, Woodbury, N. 3., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No. Drawing. Application November 8, 1933, Serial No. 697,111

10 Claims. (Cl. 524

This invention relates to improved ignition ignition of this material, so that it is necessary compositions and more particularly to such comto use an additional ignition charge. As such a positions adapted for use as the top charge in charge,-mixtures of lead sulfocyanate with oxidizelectric blasting caps. ing agents and fuels have been used, .as well as 5 Ignition compositions of the type covered by lead hypophosphite compositions, nitrocellulose 5 this invention have numerous applications. For by itself, and many other compositions, both in example, they may be used advantageously as the loose and compressed formtop charge in composition blasting caps, both of The object of my invention is a new and imthe ordinary fuse type, where the ignition charge proved ignition composition having highly deis fired by the spit of a fuse, and in electric sirable properties.- A'further object is a com- 10 blasting caps, in which the initiation of the igniposition that is compatible for use with the mation charge is brought about by means of the heat terials ordinarily employed for cap shells. A developed by the passage of an electric current still further object is a composition well adapted through a bridge wire of very small diameter. A for ignition by electrical means because of its second use is as the ignition charge in electric low firing current requirements. Additional obl5 squibs, which are adapted to bring about the ex- .iects will be disclosed as the invention is further plosion of deflagrating explosives such as black described. powder, and which require an ignition charge I have found that the foregoing objects are developing a considerable flame. A third use is accomplished by the use, as an ignition composiin igniters generally, particularly those of the tion, of nitro-cellulose impregnated'with aliquld 0 match head type. In this case, the ignition maexplosive nitric ester. Various liquid nitric esters terial may be cemented to the firing bridge wire are suitable for the purpose intended, for exby forming the ignition composition into a paste ample nitroglycerin, ethylene glycol dinitrate, with various solvents. If so desired, the composinitrochlorhydrins, and the like. Preferably, howtion may be subsequently coated and waterproofed ever,- I employ nitroglycerin as the liquid nitric by solutions of nitrocellulose. ester, because of its favorable properties and Blasting caps of both the fuse and electric its availability. Similarly, various kinds of nitrotypes, as commonly used, are of the class called cellulose may be utilized as the material for imcomposition caps, in that they contain more than pregnation. I prefer, however, to use nitroone explosive charge, for example a base .or seccotton, and particularly a nitrocotton in the form ondary charge at the closed end of the metal of smokeless p w in comminl-lted conditionshell container and a primary charge superim- The material known as Pyro' powder, in ground posed on the secondary charge. As secondary form, has been found to be very satisfactory for detonating compounds, tetranitromethylaniline use.

(tetryl), trinitrotoluene, pentaerythrite tetrani The impregnated nitrocellulose material, by

trate, picric acid, diazodinitrophenol and the like itself, gives an ignition composition that has have been most commonly used, while the pridesirable properties in many respects. It is mary charges'have customarily comprised mernot altogether satisfactory, however, from the 4 cury fulminate, either alone or mixed with an point of view of speed of burning and firing cur- 40 oxidizing agent such as potassium. chlorate, and rent requirements, when intended for ignition lead 'azide. The use of either mercury fulminate by electrical means. I prefer, therefore, to inor lead azide in .metal shells at times involves corporate with the impregnated nitrocellulose certain disadvantages due to the actio'n of these an inorganic salt, preferably an oxidizing salt,

materials on the shell wall. Lead azicle for exfor example sodium nitrate, sodium nitrite, p'o- 45 ample, can not be used in open copper shells tassium nitrate, potassium chlorate, potassium because of the formation of supersensitive copper perchlorate and the like. Various non-oxidizing azide. Mercury fulminate, on the other hand, is salts, however, may also be used, such as sodium not desirable for use in similar shells of aluminum chloride and potassium chloride. I find pobecause of the usual presence of small amounts tassium chlorate to be the most desirable of the 50 of free mercury in the material, which tends to inorganic materials mentioned. form amalgams with the metal and thus disin- Various compositions of the ingredients listed tegrate it. heretofore, may be used. Preferably, however,

When lead azide alone is employed as the pri- I employ a charge within the limits of 40-80% 65 mary charge, difliculty is frequently. met in the smokeless p wder, nitroglycerin and 225% potassium chlorate. As a suitable composition, I may cite the following:-

Percent Smokeless powder 63 Nitroglycerin 27 Potassium chlorate 10 While the compositions, according to my invention, may be used as an ignition charge in is as a top charge in electric blasting caps, either as the primary charge itself, without a special ignition charge, or as the ignition charge above the primary charge. When used as a primary charge, my ignition composition will be superimposed on a base charge of tetryl or other suitable detonating compound. If desired, however, a base charge of any suitable material may be used, with a primary charge above, of lead azide for example and a top ignition charge of the composition described in the foregoing. A charge consisting of 63% smokeless powder, 27% nitroglycerin, and 10% potassium chlorate, for example, is readily ignited by the hot bridge wire of an electric blasting cap, requiring a firing current of only 0.358 amperes. In addition, such a. composition possesses a relatively high initial velocity of combustion, so that it rapidly picks up to its maximum speed.

My impregnated smokeless powder charge is similarly adapted for use in electric squibs, where it gives very favorable results, since it is readily brought to ignition electrically by the bridge wire and possesses the flame producing qualities required in the case of squib compositions. For similar reasons, such compositions are satisfac tory as ignition charges for igniters of the match head type.

The compositions according to my invention may be prepared in various ways. I have found an eflective method of bringing about the desired results to comprise mixing Pyro powder with water in such a manner as to cause it to become thoroughly wet. Nitroglycerin is then added slowly, while the suspension is agitated for several hours. I find a suitable ratio of the ingredients to be 150 parts by weight of Pyro powder, 675 parts of water and 66 parts of nitroglycerin. After the agitation of the ingredients in the manner described, the nitrocellulose becomes thoroughly impregnated with the nitroglycerin. The impregnated nitrocotton is filtered on a suction filter to a moisture content of about 25%. time, the material is mixed with the inorganic salt, for example potassium chlorate, a suitable amount of the latter being 24 parts by weight. The water present in the material tends to dissolve the potassium chlorate, thereby bringing At thisabout at least a partial impregnation with this salt, as well as with the nitroglycerin. The material, after being screened and dried is in a form suitable for loading into blasting caps. When dry, it is relatively free running, and has no tendency to be lumpy.

The ignition composition, prepared according to my invention possesses various features of novelty and many desirable properties. It makes possible the use of a sensitive liquid explosive ingredient in such compositions, without any of the disadvantages ordinarily associated with liquid ingredients under such use. The addition of the inorganic salt tends to give grains of higher density, better free-running properties, and a composition of lower firing current requirements.

I have described my invention in considerable detail in the foregoing, but it will be understood that there may be many modifications in the proportion of the ingredients present and in the method of treatment, without departing from the scope of the invention. I intend to be limited, therefore, only by the following claims.

I claim:

1. An ignition composition comprising nitrocellulose impregnated with a liquid explosive nitric ester.

2. An ignition composition comprising nitrocellulose impregnated with nitroglycerin.

3. An ignition composition comprising nitrocellulose impregnated with a liquid explosive nitric ester, said impregnated material being intimately associated with an inorganic salt.

4. An ignition composition comprising nitrocellulose impregnated with a liquid explosive nitric ester and with an inorganic oxidizing material.

5. An ignition composition comprising nitrocellulose impregnated with nitroglycerin and with potassium chlorate.

6. An ignition composition comprising comminuted smokeless powder, impregnated with nitro glycerin and with an inorganic oxidizing salt.

'7. An ignition composition comprising smokeless powder impregnated with nitroglycerin and potassium chlorate, said charge comprising 40-80% smokeless powder, 5-35% nitroglycerin, and 225% potassium chlorate.

8. An ignition composition as the top charge in a composition blasting cap, comprising smokeless powder impregnated with nitroglycerin and an inorganic oxidizing salt.

9. An ignition composition as the top charge in a composition electric blasting cap containing a base charge of a secondary detonating compound, said ignition composition comprising smokeless powder impregnated with nitroglycerin and with an inorganic oxidizing salt.

10. An ignition composition as the top charge in an electric blasting cap containing a base charge of a secondary detonating compound, said ignition composition comprising smokeless powder impregnated with nitroglycerin and potassium chlorate and having the composition 40 to 80% smokeless powder, 5 to 35% nitroglycerin, and 2 to 25% potassium chlorate.

CHARLES P. SPAETH. 

